For a given configuration, an Internal Combustion Engine (ICE) operating at a higher altitude tends to reach higher temperatures as compared to the engine operating at a lower altitude when producing a same amount of power. This may cause overheating of engine components, such as, for example valves, pistons, and other in-cylinder components associated with the engine. Overheating may in turn lead to premature failure of the valve. In order to prevent overheating, the engine is derated by reducing a fuel supply to the engine. Typical calibration strategies consider constraints such as exhaust gas temperature, peak cylinder pressure, turbocharger speed, compressor outlet temperature, and smoke opacity. Such strategies fail to consider a temperature of the valve, a piston, a liner, a cylinder head, and a pre-chamber, which in some situations may be a limiting factor in the system.
Some prior attempts to account for the valve temperature limitations include correlating it with the exhaust gas temperature. Such an approach is typically inaccurate, since the valve temperatures are more aligned with peak cylinder temperatures during a cycle than the exhaust gas temperature. Other derate strategies may involve advancing injection timing for the sake of reducing the exhaust gas temperature. This may lead to a more substantial pre-burned spike, relatively higher exhaust gas temperatures and in turn cause an increase in the temperature of the valve.
U.S. Pat. No. 5,483,941 discloses a method for use with a vehicle including a multi-cylinder internal combustion engine having exhaust valves. The method controls the temperature of the exhaust valves during fuel cutoff modes of engine operation utilizing a bit pattern representation of the engine cylinders. The method includes cutting off the fuel delivered to the cylinders in an indexed cylinder firing pattern to vary which cylinders receive fuel so as to maintain acceptable exhaust valve temperature levels. The method may also include operating the engine with a lean air/fuel ratio so as to maintain acceptable catalytic converter temperature levels.